I'm looking for ideas - I have a 2018 Thor Chateau C class 28E motorhome. On three occasions the engine has failed to start due to what appears to be a dead battery. This happens after the rig is in use, plugged in to shore power, after 3-5 days. The rig has been checked and I'm told no problems were found. The last time I was able to use emergency start to get it going, but I'm frustrated when I can't be sure if the unit will start. Other than this, all systems operate properly. Any ideas?

Almost no Class C's are set up from the factory to charge the chassis battery via shore power. A LOT of owners install a charger just for that reason. Google up "TRIK-L-START" to view an example. I installed that one and it was a breeze. There are others available.It could be that your battery is faulty, but not likely ..... as new as it is. To rule that out, you may want to take your battery out of the rig and have a local parts house give it a load test. They do that for free.Another option is to install a chassis battery disconnect ..... for when you are not going to use the coach for a few days (or for winter storage.) Amazon has at least a couple of styles. I will try to attach a pic of mine .... (may end up with just a link.) I open that switch just as religiously as I shut off the "salesman's" switch for the coach batteries. Never any "surprises" with that protocol. lolGood luck with your fix ...... and safe travels.https://photos.google.com/album/AF1QipPVZNDABfllStoPEY--AFTPvv4ZrxJkfFAtz95U/photo/AF1QipPmhoUdl-5d_7fwea8WxzGal1Oy94wvXcVjiS-T

We have an older (2007) Thor model. We've also had the battery go down, but not in 3 days.The shore power does not connect to the truck battery.I've heard that if you don't go out through the driver's door the little bits on the dash and stuff stay on. We once had the battery die because I left the GPS plgged into the cigarette lighter for 3 weeks.I used to suspect that the heaters for the outside mirrors were switched on -- I didn't know which way was off.

When you reach your destination and setup, are you using any chassis electrical connections? This could be using some plug in inverter through the cab's power port or similar use? Are you connecting any 12 volt power directly to the chassis battery? Do you leave any chassis electrical systems powered up such as dash infotainment system, dome lights, etc?

Just wondering if there is some type of battery isolator that has failed. There usually is a steady current draw from the radio from it's keep alive memory, plus other things as suggested. If you get a clamp-on amp meter you can measure the current draw, you can also measure it with a voltmeter, then while you watch the amp meter pluck each fuse in and out till you see the current stop. That's the offending circuit.

TRIK-L-STARTBefore you do anything, make sure your battery cables are clean and tight.

Intermittent failure to start. | Good Sam Community

T18skyguy
Explorer
Apr 20, 2019
Just wondering if there is some type of battery isolator that has failed. There usually is a steady current draw from the radio from it's keep alive memory, plus other things as suggested. If you get a clamp-on amp meter you can measure the current draw, you can also measure it with a voltmeter, then while you watch the amp meter pluck each fuse in and out till you see the current stop. That's the offending circuit.
ItsyRV
Explorer
Apr 20, 2019
When you reach your destination and setup, are you using any chassis electrical connections? This could be using some plug in inverter through the cab's power port or similar use? Are you connecting any 12 volt power directly to the chassis battery? Do you leave any chassis electrical systems powered up such as dash infotainment system, dome lights, etc?
DavidandDayle
Explorer
Apr 20, 2019
We have an older (2007) Thor model. We've also had the battery go down, but not in 3 days.
The shore power does not connect to the truck battery.
I've heard that if you don't go out through the driver's door the little bits on the dash and stuff stay on. We once had the battery die because I left the GPS plgged into the cigarette lighter for 3 weeks.
I used to suspect that the heaters for the outside mirrors were switched on -- I didn't know which way was off.
youracman
Explorer
Apr 20, 2019
Almost no Class C's are set up from the factory to charge the chassis battery via shore power. A LOT of owners install a charger just for that reason. Google up "TRIK-L-START" to view an example. I installed that one and it was a breeze. There are others available.

It could be that your battery is faulty, but not likely ..... as new as it is. To rule that out, you may want to take your battery out of the rig and have a local parts house give it a load test. They do that for free.

Another option is to install a chassis battery disconnect ..... for when you are not going to use the coach for a few days (or for winter storage.) Amazon has at least a couple of styles. I will try to attach a pic of mine .... (may end up with just a link.) I open that switch just as religiously as I shut off the "salesman's" switch for the coach batteries. Never any "surprises" with that protocol. lol

Good luck with your fix ...... and safe travels.

https://photos.google.com/album/AF1QipPVZNDABfllStoPEY--AFTPvv4ZrxJkfFAtz95U/photo/AF1QipPmhoUdl-5d_7fwea8WxzGal1Oy94wvXcVjiS-T

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Intermittent failure to start.

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